1. Field of the Invention
The present invention relates generally to lighting control, and particularly to toggle switch and variable actuator control mechanism.
2. Technical Background
A toggle switch in combination with a variable actuator control mechanism, e.g., a dimmer, is a device that controls a load with two separate actuators. One of these is a single pole single throw (SPST) switch or a single pole double throw (SPDT) switch. The SPST is an ON-OFF switch that may be connected to a single electrical load or multiple loads in parallel. The SPDT switch may be employed to switch between two loads, i.e., when one load is ON, the other load is OFF, and vice-versa. Two SPDT switches may be employed in combination to control a single load from two separate locations. In each of these examples, a load, such as a lighting device, is either ON or OFF. In addition to the toggle switch, many consumers often prefer a control mechanism that includes a variable actuator control mechanism configured to efficiently control the amount of power being provided to the a, e.g., the intensity of the emitted light. The user may adjust the variable actuator control mechanism setting as needed or as desired. Some variable actuator control mechanisms include automatic variable actuator controls that adjust the light intensity based on ambient light conditions.
A variable actuator control mechanism, such as a dimmer, may be implemented using an RC control circuit in combination with a thyristor such as a TRIAC. The TRIAC is a bidirectional electronic switch that is configured to conduct current in either direction when it is turned ON. The TRIAC may be turned ON by applying a positive or a negative voltage to the TRIAC gate. The TRIAC is a very convenient way to control the amount of AC power consumed by the lighting device because the TRIAC may be turned ON and OFF in response to a pulsed signal applied to the gate. In practice, the ON/OFF cycle of the TRIAC is often controlled by an RC circuit. The resistor portion of the RC circuit is typically implemented using a potentiometer. A potentiometer is a resistor with a sliding contact that forms an adjustable resistance value. The potentiometer is employed by the user to adjust the value of the resistance to thereby change the RC time constant of the RC circuit. Thus, when 60 Hz AC power is applied to the RC circuit, the RC time constant is adjusted via the potentiometer to adjust the duty cycle of the control signal applied to the gate of the TRIAC. When the duty cycle is relatively low, the TRIAC is ON for a relatively small portion of the AC cycle and the light is relatively dim. When the duty cycle is relatively high, the TRIAC is ON for a relatively long portion of the AC cycle and the light appears to be relatively bright. In addition to lighting control circuits, TRIACs may also be employed in speed control circuits for electric motors (e.g., electric fans) and other appliances.
One of the issues of concern to variable actuator control mechanism designers relates to the thermal energy generated by the electrical components of the device. The TRIAC, in particular, generates a significant amount of heat. This concern is exacerbated in toggle switch and variable actuator control mechanisms that include the switch control and variable actuator control within a standard NEMA No. 1 cover plate opening i.e., 0.925″ (minimum) high by 0.401″ (minimum) wide, because the electrical components tend to be disposed within a central region of the device housing. One common technique for mitigating the thermal energy generated by the components is to mount the TRIAC on a heat sink/ground plane. While the heat sinking of the TRIAC improves the thermal performance of the device, the side of the TRIAC opposite the heat sink is not thermally isolated from the interior of the device housing. What is needed, therefore, is a toggle switch/variable actuator control combination switch designed for a standard NEMA No. 1 cover plate opening that more effectively isolates the TRIAC from the device interior and spatially separates the electrical components to obtain improved thermal performance.
Another issue that is of concern relates to the costs associated with the toggle dimmer assembly. In state of the art devices, the front body member typically includes a framed portion that accommodates both the toggle switch and the dimmer actuator. The toggle actuator and the dimmer actuator are typically fabricated as separate pieces that extend through their respective framing slots and mate with their respective interfaces on the circuit board. One drawback to this approach relates to the time associated with assembling the various and disparate pieces (including the actuator pieces, the interface pieces, etc.). Thus, what is needed is a modular switching assembly that easily incorporates the various pieces of the toggle dimmer assembly such that the entire modular assembly may be snapped in place on the printed circuit board. This approach saves time and therefore money.